If I saw the webpage saying my email address is registered, I'd try to use
the 'lost password' tool and see if it sends me the option to set a
password. If that happened and worked, then from his account on groups.io he
could find the group and register that way (I think).
-Ken Cameron, Member JMRI Dev Team
www.jmri.org
www.fingerlakeslivesteamers.org
www.cnymod.org
www.syracusemodelrr.org
[Mode note: You don't register for a group, you subscribe.]
Ken Cameron